5 Answers
5

Here's a brief overview to get you started. Hopefully others will answer with some more details too.

'Gain' controls are typically used to get a good input level. So for example if you had a microphone with a very low output signal, you would boost the gain to get a better level into your mixing desk or audio interface. If you had a synthesizer plugged in you might need to turn the gain down to stop the signal distorting. Gain controls are often controlling an amplifier behind the scenes - i.e. your signal can 'gain' strength after going through the gain stage of your audio equipment. So gain is usually the first control in the signal path of your recording equipment.

'Volume' controls on the other hand tend to be at the end of the signal chain and are more likely to be attenuating rather than amplifying the signal. So on a mixing desk, having got a good level from each input at the gain stage, you use the volume faders to adjust the relative volumes of each channel to achieve a good mix. You are not typically amplifying those signals any more though.

A guitar amp is a good example of how this works. The first control is often called "Gain" or 'drive' and guitarists often deliberately turn this really high to get a nice distorted sound from a tube preamp. However, the final control is called Volume and governs simply how loud the sound coming out of your speaker is. With gain right up and volume low you can play distorted sounds without annoying the neighbours. With gain low and volume high you get a loud sound but no distortion.

Gain staging is one of the most important things you can do to maximize the signal to noise ratio of your studio or PA set up. To set up your system so that every link in the chain, from source to speakers, is sending the maximum about of signal but not clipping, insures that you are minimizing the amount of noise reaching your amp (or recorder). The Yamaha Pa rep for the Midwest used to do this dramatic demo where he would take program material and play it really loudly through a large PA array. Because he had gain staged correctly, when he brought down the faders, there was practically no hiss whatsoever. Compare that to most venues when you can hear hiss over extremely loud music.

In simplest terms, the gain is used to adjust the strength (i.e. voltage level) of the signal, whether that be within the electrical components of the mixing board, within the software DAW, signal sent to magnetic tape, etc. Volume, on the other hand, is used to adjust the loudness of the signal as you perceive it, whether that is through speakers, or headphones, etc.

Gain = internal voltages

Volume = perceived loudness

Clearly, these two are inter-related. Also, keep in mind that not all equipment maintains the distinction in their labeling.

This is a little outdated of a label, but TO TAPE would be the signal flow getting the audio you're wanting to record to the storage device - it used to be actual reels of tape, now it's typically a hard drive. This is where GAIN comes into play. Gain is the control that governs how 'hot' a preamp is being driven TO TAPE. When you store that audio data, the gain is typically the level a given track is recorded at.

Volume on the other hand, is simply an attenuation that has no bearing on the stored raw audio. Volume settings can be stored, but it's impact is not placed on the stored data (audio). I could be mistaken on this last bit, but I've always understood "Volume" controls to ONLY attenuate and not amplify.

If you think of a CD that you play on your car stereo, gain was used in the preamps to get the audio recorded... volume is how loud you play it in your car. The data on the CD isn't affected, but you experience a difference in perceived loudness.

I would like to add this little bit of information, which might be useful but is probably just (somewhat) interesting ;-)

In many modern DAW's, you'll find that the Volume Controls also can work as gain, as they're by default set at 0 dB and you would normally only pull the down, but you can also push them past the 0 dB at which moment you'd use the volume control to amplify the signal.

The difference between the two, would then be that the gain is usually at the beginning of the chain while your gain achieved with the volume would usually be at the end of the chain.